The present invention relates to transducers and more particularly to piezoelectric devices utilized for the reception of acoustic waves in a submarine environment. More specifically, the invention concerns a hydrophone having a cardioid-shaped directional lobe for selective reception of acoustic waves coming from a specific direction.
In the field of acoustics, there has been considerable research conducted for the purpose of obtaining a hydrophone having directionality of the "cardioid" type. In particular, omnidirectional and bidirectional hydrophones have been combined but this type of hydrophone requires the use of an electrical circuit for balancing. These devices have the disadvantage that a considerable volume of equipment is required rendering them undesirable for certain applications.
In addition, when operating in a submarine environment, many other problems arise and the equipment may have to be modified giving particular consideration to the various materials used. Apparatus has been proposed which operates under the effect of two pressures, one supported by the front face of a flexible lamina and the other by the rear face. However, none of these devices produce a phase displacement such that, when the transducer receives an acoustic wave coming from the rear, the effect on the lamina is negligible.
An object of the invention is to obtain a hydrophone exhibiting directionality of the cardioid type having a single lobe at low frequencies, and which employs a single transducer having reduced space requirements. Such a device is useful in underwater detection and localization systems employing acoustic buoys.